Method and apparatus for loading a dredging vessel with dredging spoil

ABSTRACT

For loading a dredging vessel upto its maximum conveying capacity the weight of the load is measured, wherein a distinction is made between the dredging spoil being in settled and the dredging spoil being in fluidized condition. The magnitude decisive of the stability of the dredging vessel with its load is calculated. The calculated value is compared with the inadmissible value of the magnitude for determining the end of the loading process.

United States aten Wolters et a1.

[ 1 Oct. 17,1972

METHOD AND APPARATUS FOR LOADING A DREDGING VESSEL WITH DREDGING SPOIL Inventors: Tjako Aaldrik Wolters, Vianen; Romke van der Veen, l-lesselaan,

both of Netherlands Assignee: Ballast-Nedam Groep N.V., Amsterdam, Netherlands Filed: May 14, 1971 Appl. No.: 143,440

Foreign Application Priority Data May 14, 1970 Netherlands ..70.06965 U.S. Cl ..2l4/l5 B, 114/26, 214/152 Int. Cl ..B65g 27/00 Field of Search ..214/12, 13, 14,15 R, 15 B, 214/152; 114/26, 27, 121; 37/54, 58, 59

References Cited UNITED STATES PATENTS Norton et a1. ..1 14/121 7 the-loading process 3,329,808 7/l967 Fisher ..2l4/14 X 3,630,400 12/1971 De Koning ..214/l5 B X 3,631,997 l/1972 De Koning ..1 14/26 X Primary Examiner-Gerald M. Forlenza Assistant Examiner-Frank E. Werner Attorney-Snyder & Butrum [57] ABSTRACT For loading a dredging vessel upto its maximum conveying capacity the weight of the load is measured, wherein a distinction is made between the dredging spoil being in settled and the dredging spoil being in fluidized condition.

The magnitude decisive of the stability of the dredging vessel with its load is calculated.

The calculated value is compared with the inadmissible value of the magnitude for determining the end of 4 C ai 8, q wietiiser PATENTEDnm 11 m2 SHEET 1 UF 6 INVENTOR AAA D? K Wa; 75 3 ATTORNEY PATENTEDHBI 17 I972 3.698.573

sum 2 0F 5 FIG.3A

INVENTOR ATTORNEY PATENTEDnm n ma SHEEI 3 OF 6 INVENTOR ATTORNEY PATENTEDnm 11 1972 SHEET 5 [IF 6 INVENTOR kb M n' v/M/ V155 ATTORNEY METHOD AND APPARATUS FOR LOADING A DREDGING VESSEL WITH DREDGING SPOIL The invention relates to a method of loading a dredging vessel with dredging spoil by supplying a suspension of dredging spoil with water to a hold of the dredging vessel and by draining off mainly water from the hold.

In the known method of the above mentioned kind generally the dredging vessel is not loaded unto its maximum conveying capacity. For considerations of stability a fair safety margin based on experience figures is introduced when loading.

The invention provides a method of loading the dredging vessel'each time unto its maximum conveying capacity with various kinds of dredging spoil, while yet observing the stability. To this end the method according to the invention is performed in such a way, that during loading each time the arrangement in weight in vertical direction of the loading is picked up, wherein a distinction is made between the dredging spoil being in settled and the dredging spoil being in fluidized condition, that a magnitude decisive of the stability of the dredging vessel with its load is calculated, wherein the arrange-ment in weight and the condition of the dredging spoil of the load is discounted, the calculated value of this magnitude is compared with the inadmissible value of the magnitude decisive of the stability of the dredging vessel with its load and that when the calculated value approaches the inadmissible value the loading operation is controlledfor avoiding that the inadmissible value is reached.

For making a distinction between the settled and the fluidized condition of the load, fluidizing fluid is periodically-supplied to the hold on a plurality of pick up places lying on different levels, the pressure of the fluidizing fluid supplied to the pick up places is picked up and the condition of the load at the relating pick up place is deduced from the pressure course at the beginning of each fluidizin g fluid supply.

The invention further provides a dredging vessel comprising a hold for receiving dredging spoil, being characterized by first pick up means for picking up the arrangement in weight in vertical direction of the load, second pick up means for picking up the level of the upper surface of the dredging spoil being in settled condition, said first and second pick up means being connected to the input of a calculating device for calculating a magnitude decisive of the stability of the dredging vessel with its load, a comparing device connected to the output of the calculating device for comparing the output value of the calculating device with a value of that magnitude adjusted in advance, said comparing device delivering a signal, when the output value of the calculating device has the value adjusted in advance in the comparing device, and by at least one member controlled by the signal of the comparing device and influencing the loading operation of the dredging vessel.

These and other features of the invention will be elucidated in the following description with reference to the enclosed schematic drawing.

In the drawings:

FIG. 1 is a cross section through a dredging vessel, in which a loading situation is shown,

FIG. 2 is a cross section corresponding with Fig. l, in which the magnitude decisive of the stability is indicated,

FIGS. 3A, 3B and 3C show together a wiring diagram of a preferred embodiment of a dredging vessel according to the invention,

FIG. 4 is a top plan view of a preferred dredging vessel according to the invention, and

FIGS. 5 and 6 are a longitudinal and a cross section respectively through the dredging vessel of Fig. 4.

The dredging vessel 1 has a hold 2 being filled with dredging spoil 3 in settled condition and dredging spoil 4 in fluidized condition and having thereabove an empty space 5. The bottom of the dredging vessel is indicated with K.

F is the center of buoyancy or in other words the center of gravity of the volume of outer water V displaced by the dredging vessel.

G is the center of gravity of the dredging vessel with its load. I

I is the moment of inertia of the intersection plane 32 of the dredging vessel 1 and the water surface 6 in relation to the middle longitudinal axis 7. From the formula MF I/V follows the height MF of the imaginary point of suspension M or the metacentre point of the dredging vessel 1 above the center of buoyancy F. The metacentre height MG of the dredging vessel 1 in each loading situation is definite for the starting stability measure of the dredging vessel 1. In case of a solid, not movable load the magnitude MG decisive of the stability is calculated from the formula MG MF F K GK.

The shape of the dredging vessel 1 is such, that with a sufficient starting stability sufficient dynamic stability is provided.

When on the contrary, as in FIG. 2, the load is not completely solid, then the magnitude MG is decreased with the value M'M resulting from M'M (i X S, )/(S X V), wherein:

i is the moment of inertia of the fluid surface 8 of the fluidized load 4 in relation to the longitudinal axis 9,

S and S,,,, are the specific gravities of the fluidized dredging spoil 4 and the outer water'10 respective- For considerations of stability the magnitude M'G decisive of the stability of the dredging vessel 1 with its solid load 3 and its fluid load 4 must stay above the inadmissible value AG.

It appears from the formula for M'F that for determining the stability of the dredging vessel 1 a distinction must be made between the dredging spoil 3 being in settled condition and the dredging spoil 4 being in fluidized condition. The dredging spoil 3 is in a settled I condition, in that a grain tension is present between the dredging spoil grains, which grain tension is absent in the fluidized condition. In order to be able to calculate this distinction between fluidized and settled dredging spoil the hold 2 is considered being divided into a plurality of floors 38a, 38b, 38c, 38d, and 38e (see FIG. 1). Of these floors the distances GaK, GbK, GcK, GdK and GeK of the centers of gravity Ga-Ge to the point K are non-variable known values being recorded in stores 39a-39 (FIG. 3). Further the nonvariable known volumes Va-Ve of these floors are recorded in stores 40a-40 and the moments of inertia i i belonging to the top surfaces of the floors 38a-38e are recorded in stores 46a-46e. In the situation as shown in FIG. 1 the top surface 11 of the settled dredging spoil 3 finds itself in the floor 38d and the surface 8 of the fluidized dredging spoil 4 in the floor 38b. Tactile points 13a, 13b, 13c, 13d and 13e adjoining these floors are mounted above each other on each of four places 12A, 12B, 12C and 12D of the hold 2 lying horizontally spaced from each other (see FIGS. 1 and 3). Furthermore tactile points 14a, 14b, 14c, 14d and 142 are mounted on the same levels as, but spaced from said tactile points 13a, 13b, 13c, 13d, and 13s and moreover a tactile point 14f is mounted there near the bottom of the hold. These tactile points are purged by purgative conduits 18, 19 and 20 connected to purgative pumps l5, l6, and 17. These purgative pumps 15, 16, and 17 suck up outboard water by means of inlets 21, valves 22 and filters 23. The tactile points 13a-l3e and 14a-14 are connected with pressure pick ups 27 and 28 respectively by means of measuring conduits 24a-24 and 25a-25f via a dividing device 26. The outputs of the pressure pick ups 27 and 28 are connected with the calculating device 31 by means of signal conduits 29 and 30 respectively and the dividing device 26. Each of four tactile points 321, 32m, 32n, and 32p is arranged at the bottom of port, starboard, bow and stern respectively of the dredging vessel 1 and is connected to a pressure difference meter 33 being connected on the other side via a measuring conduit 34 to an overflow dish 35. A purgative conduit 20 of the purgative pump 17 communicates with the measuring conduit 34. The outputs of the pressure difference pick ups 33l, 33m, 33n, and 33p are connected to the calculating device 31 through signal conduits 36l, 36m, 36n, and 36p and amplifiers 371, 37m, 37n, and 37p respectively. The dividing device 26 comprises dividing members 26r-26v coupled synchronously with each other. The purgative conduit 18 is connected successively with the purgative conduits l8a-18e of the tactile points l3a-13e by means of dividing member 26r. The measuring conduits 24a-24e are connected with the pressure pick up 27 synchronously therewith. The output of the-pressure pick up 27 is connected with signal conduits 29a-29e by means of signal conduit 29 and dividing member 26t.

The tactile points 13a-13e are periodically purged by successively connecting the pump with these tactile points by means of dividing member 26r. At the beginning of each purgation the purgative fluid meets with a greater resistance, which is expressed by a stronger pressure shock picked up by the pressure pick up 27, in case the dredging spoil is in the settled condition at the place of the relating tactile point 13a13e than in case the dredging spoil is in the fluidized condition at the place of the relating tactile point l3a-l3e.

The tactile points 14a-14f are purged continuously and are connected to pressure pick up 28 by means of dividing member 26v, the output of said pressure pick up 28 being connected with the measuring value stores 41a-41 of the calculating device 31 by means of signal conduits 30 and dividing member 26a and by means of signal conduits 30a-30f. The signal conduits 29a-29e are connected to switches 43a-43s and to anadder 44 via high pass filters 42a-42e. Each pair of succeeding stores 41a and 41b to 41e and 41f inclusive is connected to subtractors 45a and 45e respectively. The outputs of the subtractors 45a-45e represent the values of the specific gravity of the material of the relating floors, said outputs as well as the stores 40a and 402 respectively of the volumes Va-Ve being directly connected with the multipliers 47a-47e and being connected via switches 43a-43c with the multipliers 48a-48 as well as the stores 46a-46e of the moments of inertia i -i In the loading situation shown in Figs. 1, 2 and 3 the surface 11 of the dredging spoil finds itself in the floor 38d between the tactile points 13d and 13a. The tactile points 13a and 13b deliver a nil signal at the choice switches 43a and 43b, the tactile points 13c and 13d deliver a fluid signal at the switches 43c and 43d. On the contrary the tactile point l3e delivers a higher starting signal, owing to which settled dredging spoil is signaled and the switch 432 is converted, so that the subtraction value (i/V)X( S,, /S,,,,) is not conducted further.

The outputs of the multipliers 47a-47e represent values relating to the weights Gw -Gw of the material of the floors 38a-38e and are lead into the adder 49 of the complete weight of dredging spoil on one of the places 12. Moreover the output signals of stores 63p, 63q, and 63r relating to the weights for oil, water and other load respectively are supplied to the adder 49. Moreover the output signals of the multipliers 62p, 62: and 62r relating to Gw X GK for oil, Gw X GK for water and Gw X GK for other load respectively are supplied to the adder 51, said multipliers being fed by the stores 63p, 63q, and 63r of the weights and the stores 64p, 641;, and 64r of the relative GK. Moreover the outputs of the multipliers 47a-47e are together with stores 39a-39 of the distances GaK-GeK connected to multipliers 50a-50e, the outputs of said multipliers 50a-50 representing the values of GaK X Gw GeK X Gw and being supplied to the adder 51 for the complete value of Gw X GK of one of the places 12. The output signals of the adders 49 and 51 of one particular place 12 are divided into each other in the divider 52, while the output signals (Gw X GK)/Gw GK of each divider 52 are supplied to the divider 54 via the adder 53, said divider 52 dividing in this case the result of four measuring places 12 into four. The output of the divider 54 is the average value GK.

The outputs of the multipliers 48a-48e represent the products i X sg i X sg They are connected to the dividers 55a-55e together with the store 56 relating to the specific gravity sg of the outboard water 10. The outputs of these dividers are supplied to an adder 57 as well as to a pulse counter 58. The output signal of the adder 57 is divided in the divider 59 through the output signal of the pulse counter 58, as soon as this pulse counter 58 receives a command from the divider 26 at the end of a measuring cycle. In a similar way the measuring value stores 41a-41f are emptied simultaneously. The output signals of the four dividers 59 are supplied to the adder 60 and after that divided in the divider 61 into four. The output signal of the divider 61 represents the value i X S /S The amplified output signals in the signal conduits 36l, 36m, 36n, and 36p enter into a selector 65 only accepting the strongest signal (of the greatest draught), said signal being compared in the subtractors 66 and 67 with the draught value to be regulated and adjusted in advance in the stores 68 and 69 and with the maximum permissible draught value respectively. The draught value to be regulated is adjusted in dependence on variable work conditions, such as the draught of the fairway. The maximum permissible draught value of the store 69 may never be exceeded for safety considerations.

Signal conduits 36l and 36 m contain signals from the starboard and port draught pick ups not shown, said signals being supplied to the subtractor 71 via conduits 70l and 70m, said subtractor 71 being connected via a two-way switch 72 with adders 73 In and 73 lp or with adders 73 mn and 73 mp. In the same way the signal conduits 36n and 36p contain signals from bow and stem draught pick ups, said signals being supplied to the subtractor 74 via conduits 70n and 70p, said subtractor 74 being connected via a two-way switch 75 with adders 73 In and 73 mn or with adders 73 lp and 73 mp. The two-way switches 72 and 75 are controlled by the difference of the signals in the signal conduits 761; 76m and 76n;76p respectively.

Moreover the adders 73 In, 73 mn, 73 lp and 73 mp receive a signal from an adder 77 being fed by the output signal of the subtractor 66 for the draught to be regulated and by the output signal of a subtractor 78. The subtractor 78 compares the value of MG calculated at the relative loading situation with the permissible stability value MG being adjusted in advance in the store 79.

The signal conduits 361, 36m, 36n, and 36p feed an adder 80, The output signal thereof is divided in divider 81 into four for obtaining the average draught and controls then the motor 84 for driving a'step switch 82 being provided with three rings 821, 82V and 82F. These rings carry the contacts of the stores 83], 83V and 83F, which contain fixed values relating to the moment of inertia I, the distance PK and the volume V of the dredging vessel 1, which belong to the occurring draughts lying between the minimum and .the maximum draught.

The signal of inertia picked up by the tactile member 85I is divided in the divider 86 through the belonging volume signal coming from the tactile member 85V and is then supplied to a subtractor 87. The signal coming from the divider 61, which represents the value i x S is divided in the divider 88 through the volume signal of the tactile member 85V. This quotient (i/V) X (S /S is then subtracted in subtractor 87 from (IN) the output signal of divider 86, so that the signal (I/V) (i/V) X (S /S is obtained. This signal is supplied together with the signal for FK coming from the tactile member 85F to an adder 89, so that then the value FK (I/V) (i/V) X S /S is obtained, which is decreased in the subtractor 90 with the value GK coming from the divider 54 for obtaining a magnitude M G decisive of the stability:

This calculated magnitude is supplied to the subtractor 67, just like the inadmissible value adjusted in the store 79 of the magnitude MG decisive of the stability. When the calculated value for M'G from the subtractor 90 approaches the magnitude MG from the store 79 the loading operation of the dredging vessel 1 is regulated for avoiding that the inadmissible value of this magnitude is reached.

The output of the subtractor 90 is further connected to the subtractor 91 together with the store 99 of a value stopping the loading process.

The outputs of the subtractors 67 and 91 are therefore connected via signal conduits 92 with a stopping device for stopping the loading process.

The signal conduits 93 In, 93 mn, 93 lp and 93 mp coming from the calculating device 31 control the valves 98 In, 98 mn, 98 lp and 98 mp as shown in FIGS. 4 and 5.

The output signal of the adder 44 being fed by the high pass filters 42a-42e, is supplied to the adder 94 together with the corresponding output signals of the three other places 12. The output signal of the adder 94 is divided in the divider 95 into four for obtaining the average column height of the settled dredging spoil 3. The signal conduit 96 coming from the calculating device 31 and being connected to the divider 95 controls the jack 97 of a dredging spoil supply 100 as shown in FIG. 5.

The dredging vessel 1 shown in FIGS. 4, 5 and 6 has a pump 101 sucking up a suspension of dredging spoil and water via a suction pipe 103 and bringing this suspension via a pressure pipe 102 and a telescopic supply 100 into the loading hold 2. In the drawn loading situation the dredging spoil 3 is settled and fluidized dredging spoil 4 stands thereabove. Water is sucked away from under the surface 8 of the dredging spoil 4 by means of siphons 104 I ln, 104 mn, 104 1p, and 104mp. Each siphon consists of a nozzle 106 being variable in level and driving with a float 105 on the fluidized dredging spoil, a flexible conduit 107 and a standing conduit 108 ending in the outboard water and having a valve 98. The valve 98 is controlled by means of a jack 109. In order to have the dredging spoil sunk particularly there,.where the draught of the dredging vessel 1 is the smallest, the signals delivered by the signal conduits 93 lp, 93 In, 93 rm and 93 mp control the jacks 109 and further jacks 110 of supply valves 111lp,11lln,111 mn, and 111 mp in such a manner, that a suspension flow 112 is directed from the supply 100 to the nozzle 106 of the siphons 104 lp, 104 In, 104 nm and 104 mp, where the draught is the smallest.

As a result of the supply of the suspension from the lower side and on the gradually rising level 11 of the settled dredging spoil 3 the supplied suspension has only little kinetic energy when entering into the loading hold 2, so that the settling is optimum.

The signal conduit 92 coming from the calculating device 31 is connected to a jack 113 of the control of the valves 114 and 115 coupled to each other for leading the suspension sucked up into the loading hold 2 or for leading this suspension overboard.

What we claimed is:

1. Method of loading a dredging vessel with dredging spoil by supplying a suspension of dredging spoil with water to a hold of the dredging vessel and by draining off mainly water from the hold, characterized in that during loading each time the arrangement in weight in vertical direction of the loading is picked up, wherein a distinction is made between the dredging spoil being in settled and the dredging spoil being in fluidized condition, that a magnitude decisive of the stability of the dredging vessel with its load is calculated, wherein the arrangement in weight and the condition of the dredging spoil of the load is discounted, the calculated value of this magnitude is compared with the inadmissible value of the magnitude decisive of the stability of the dredging vessel with its load and that when the calculated value approaches the inadmissible value the loading operation is controlled for avoiding that the inadmissible value is reached.

2. Method as claimed in claim 1, characterized in that for making a distinction between the settled and the fluidized condition of the load fluidizing fluid is periodically supplied to the hold on a plurality of pick up places lying on different levels, the pressure of the fluidizing fluid supplied to the pick up places is picked up and the condition of the load at the relating pick up place is deduced from the pressure course at the beginning of each fluidizin g fluid supply.

3. Dredging vessel comprising a hold for receiving dredging spoil, characterized by first pick up means for picking up the arrangement in weight in vertical direction of the load,

second pick up means for picking up the level of the upper surface of the dredging spoil being in settled condition,

said first and second pick up means being connected to the input of a calculating device for calculating a magnitude decisive of the stability of the dredging vessel with its load,

a comparing device connected to the output of the calculating device for comparing the output value of the calculating device with a value of that magnitude adjusted in advance, said comparing device delivering a signal, when the output value of the calculating device has the value adjusted in advance in the comparing device,

and by at least one member controlled by the signal of the comparing device and influencing the loading operation of the dredging vessel.

4. Dredging vessel as claimed in claim 3, characterized in that the second pick up means comprise a plurality of tactile'members lying on different levels, being connected to a source of fluidizing fluid by means of fluidizing conduits including valves periodically controlled and being connected to a pressure sensitive pick up by means of a tactile conduit, said pick up being connected to a store registrating a pressure shock. 

1. Method of loading a dredging vessel with dredging spoil by supplying a suspension of dredging spoil with water to a hold of the dredging vessel and by draining off mainly water from the hold, characterized in that during loading each time the arrangement in weight in vertical direction of the loading is picked up, wherein a distinction is made between the dredging spoil being in settled and the dredging spoil being in fluidized condition, that a magnitude decisive of the stability of the dredging vessel with its load is calculated, wherein the arrangement in weight and the condition of the dredging spoil of the load is discounted, the calculated value of this magnitude is compared with the inadmissible value of the magnitude decisive of the stability of the dredging vessel with its load and that when the calculated value approaches the inadmissible value the loading operation is controlled for avoiding that the inadmissible value is reached.
 2. Method as claimed in claim 1, characterized in that for making a distinction between the settled and the fluidized condition of the load fluidizing fluid is periodically supplied to the hold on a plurality of pick up places lying on different levels, the pressure of the fluidizing fluid supplied to the pick up places is picked up and the condition of the load at the relating pick up place is deduced from the pressure course at the beginning of each fluidizing fluid supply.
 3. Dredging vessel comprising a hold for receiving dredging spoil, characterized by first pick up means for picking up the arrangement in weight in vertical direction Of the load, second pick up means for picking up the level of the upper surface of the dredging spoil being in settled condition, said first and second pick up means being connected to the input of a calculating device for calculating a magnitude decisive of the stability of the dredging vessel with its load, a comparing device connected to the output of the calculating device for comparing the output value of the calculating device with a value of that magnitude adjusted in advance, said comparing device delivering a signal, when the output value of the calculating device has the value adjusted in advance in the comparing device, and by at least one member controlled by the signal of the comparing device and influencing the loading operation of the dredging vessel.
 4. Dredging vessel as claimed in claim 3, characterized in that the second pick up means comprise a plurality of tactile members lying on different levels, being connected to a source of fluidizing fluid by means of fluidizing conduits including valves periodically controlled and being connected to a pressure sensitive pick up by means of a tactile conduit, said pick up being connected to a store registrating a pressure shock. 